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Re: The Usps Aries Calculator
From: Andrés Ruiz
Date: 2010 Nov 8, 08:12 +0100

The calculation itself is simple:

GHA Aries = Sidereal Time At Greenwich.

JD: Julian day

T = (JD - 2451545.0 ) / 36525.0;

theta0 = 280.46061837 + 360.98564736629*(JD-2451545.0) + 0.000387933*T*T - T*T*T/38710000.0;

theta0 = ang_0_360(theta0);

GHA = theta0 + deltaPsi*COS( epsilon );

The term deltaPsi*COS( epsilon ), take account of Nutation, obliquity of the ecliptic.

And can be ignored if the accuracy of ±0.02' is not necessary

Do 0<= GHA <= 360

And of course Local Sidereal Time: LHA = GHA + L

At my Website at [Papers][ Under Development] “Astronomía de Posición” more information in english about JD and LST can be found.

Regards,

Andrés Ruiz

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